Exhaust gas silencer



Sept. 1, 1931.

F. F. HAMILTON EXHAUST GAS SILENCER Filed Feb. 7, 1929 2 Sheets-Sheet l.

Sept; 1, 1931. v F. F. HAMILTON 1,821,013

EXHAUST GAS SILENCER Filed'Feb. 7, 1929 2 sheets-sheet 2 'Q n MM rz i o //L 'Y 1 Il l' n I -a '9 UNlTED STATES PATENT Price FRANCIS F. HAMILTON, '0F INDIANAPOLIS, INDIANA, ASSIGNCR T0 HAMILTON MUFFLER COMPANY, GF INDIANAPOLIS, INDIANA, A CORPORATION OF NDIANA EXHAUST GAS SILENCER Application4 filed February 7, 1929.

rlhis invention relates to the art of niuffling xhaust gases and while of general adaptation, finds a particular application in the automotive iield. Many mufflers have been designed and built for use, for instance on automobiles, and yet in spite of the great amount of work that has been done heretofore, the objection has universally been that to secure silence, the muiier seriously retarded the flow of exhaust gases from the engine by reason of considerable backpressure, and that in eliminating that back pressure, silence was sacrificed and too much noise emanated from the gases.

It is the primary object of this invention to eliminate substantially all of the noise as well as the back pressure in a very simple structure, light in weight, readily assembled from a minimum number of rolled or stamped steel or iron parts, that will not be conducive to back-lire, and that will be exceedingly substantial and durable over a long period of time.

Other objects will be readily apparent in the following description of the invention made in reference to the accompanying drawings, in which- Fig. 1 is a fragmentary side elevation of a muffler embodying the invention;

Fig. i2, a Vertical transverse section on the line 2 2 in Fig. 1;

Fig. 3, a fragmentary side elevation of a modified form of a muii'ler embodying the invention;

4, a vertical transverse section on the line 4-4 in Fig. 3;

5, a fragmentary side of a muffler slightly modified from that forni as shown in Fig. 1;

Fig. 6, a vertical, transverse section on the line 6 6 in Fig. 5; and

Fig. 7, a detail in fragmentary side elevation of the exhaust head structure as employed in the form shown in Figs. and 6.

Like characters of reference indicate like parts throughout the several views in the. drawings. Y

Referring iirst to Figs. 1 and 2, I forni an outer cylindrical shell 10 into which are folded a plurality of circumferential beads 11 to Serial No. 338,085.

project inwardly from the inner wall of the shell 10. These beads are spaced apart to have an interval of the straight cylindrical wall of the shell longitudinally therebetween. i p

The forward end of the shell is drawn conelike forwardly and to one side to receive therethrough eccentiically of the longitudinal axis of the shell 10, the intake pipe 12.

The intake pipe 12 extends a substantial w distance within the shell 10 and receives the forwardly projecting annular boss 13 in the end of the pipe. The boss 13 is an integral part of and is located eccentrically on the plate 14 which has an annular flange 15 pro- A the pipe 12 as to cause the wall of the tube 16 to be nearer the pipe 12 on the side farthest ieiiioved from the longitudinal axis of the shell 10.

The rear end of the tube 16 is closed by the plate 14 while the forward end is entirely open, the forward end terminating substantially in the same plane as that of the end of the shell 10. The pipe 12 has a plurality of perforations 17 along its side nearest the wall of the tube 16, the perforations being made substantially one-quarter of an inch in diameter.

Spaced circuinferentially around the pipe 12, are a plurality of perforations .unich smaller than the perforations 17, the perfora- .r

tions 50 being preferably substantially oneeighth of an inch in diameter. The perforatiens 17 form substantially thirty per cent and the perforations 50 substantially seventy per cent of the entire tot-al number of perforations. y

The cross-sectional area of the tube 16 less the cross-sectional area ofthe pipe 12 is equivalent to the cross-sectional area of the pipe 12, so that there is no increase in volume of the gases between those in the pipe 12 and those in the tube 16, the expansion taking place upon the gases leaving the tube 16 and passing into the shell 10. By preventing expansion between the pipe 12 and tube 16, both pipe 12 and tube 16 are kept practically lilled with gas in which the noise may be dissipated, rather than permitting the noise to reverberate within an empty hollow chamber.

The tube 16 is likewise formed with a plurality of longitudinally spaced apart circumferential beads 18 projecting to within the tube.

A tail pipe 19 is held in the rear end wall 20 which forms a rear closure to the shell 10, the end 2O being preferably concave from its inner side. rlhe tail pipe 19 projects to within the shell 10 and carries an exhaust head 21 on its forward end, the inner detailed construction of which is illustrated in Fig. 7, where a frustro-conical wall 21 flares rearwardly and Voutwardly from the end of the tail pipe 19. The wall 21 is provided with a plurality of V -shaped slots 22, and a cone 23 is inserted into the opening within the wall 21 so that gases coming through the slot-s 22 strike the cone 23 and turn rearwardly to enter into the tail pipe 19, the wall of the cone having more slope than that of the wall 21.

A frustro-conical shiell 24 is positioned around the wall 21 to define a space therebetween, the rear end of the shield being open to permit gases to enter thereunder and travel to said slots 22. An annular opening is provided around the base of the shield 24 between the shield and the base of the wall 21 so that gases may travel therethrough and enter the space within the cone 23, the cone 23 having a solid wall so that gases may not enter from its forward side into the tail pipe 19. In 7, a plate 25 by rearwardly projecting flange 26 encloses the space forwardly of the cone 23 so that the only entrance into or discharge therefrom is by way of the said annular passage between the bases of the shield 241- and the wall 21. Referring to Fig. 1, the plate 25 is dispensed with an d a conical cover 27 is employed in its place, there being no material difference insofar as the operation of the mulller is concerned.l the difference being one of mechanical expediency as will hereinafter be explained.

Surrounding the tail pipe 19, back of the exhaust head 21, is mounted a deflector 28 flaring outwardly and rearwardly toward but not contacting the rear end wall 2O of the muffler.

It is particularly pointed out that the rear circumferential edfre of the deflector 28 is in plane spaced back of the last bead 11 in the shell 10, and that the diameter of the detlector at the edge greater than that of the inside of the bead 11, an annular opening being left between the edge of the dellector and the shell 10.

Now in operation, gas coming from an engine (not shown) operating at low speed comes through the intake pine 12 discharges through the perforations 17. some through the first encountered larger perforations 17, some further along and some at the extreme end larger perforations 17, and very little if any of the gas through the smaller perforations 50 due to the greater resistance in travelling therethrough, all of the gas, being finally discharged into the tube 16, from which the gas flows out through the open forward end to Within the shell 10 proper.

At higher speeds of the engine, more gas will discharge through the smaller perforations 50. It is more difiicult to silence the exhaust of low speed engines than of high speed, and this silencer here shown is designed to eliminate the sound at slow speeds by passing the gas through the laro'er holes, and at the same time, ample provision is made for tie escape of gas at the higher speeds through the smaller holes, whereby appreciable back pressure is eliminated at the higher speeds, practically no back pressure being obtained at low speeds. However, it is to be noted that all of the gas discharged from the pipe 12 into the tube 16 does not discharge from the tube 16 simultaneously but over a period of time by reason of the fact that that part of the gas discharging from the pipe 12 through the Erst encountered perforations reaches the forward end of the tube 1G before that part of the gas going back to discharge from the rearmost perforations trave s forwardly to reach the open end of the tube 16.

Furthermore, it is to be noted that the gas travelling forwardly in the tube 16 does not flow smoothly in longitudinally straight lines but encounters the spaced apart pro iecting beads 18. the effect of which is to cause the gas to form eddy currents with a general circumferential turbulent effect, though the body of the gas continues to move forwardly and discharges expansively into the shell 10 against the forward cone-like end where the gas strikes, and reverses to flow rearwardly in the comparatively large Yclnimher formed within the shell 10, but here again. the flow encounters the spaced. apart beads 11 and the flow is not smooth but is turbulent and full of eddy currents, a situation greatly impeding the transmission of sound, as well as causing more of the gas to reach and be cooled by the outer wall of the shell 10 than would be the case were the shell wall smooth.

This bodv of turbulent gas moves rearwardly, strikes the rear end 20 and is deflected forwardly principally by the forward face of the deflector 28. Some of the gas passes up over and around the rearmost bead 11 and down under the edge of the deilector to enter the space therebehind as a means of permitting sound to rever-berate therein until it dies out, the sound being effectually trapped therein by reason of the particular location of the deflector edge. The flow of gas enters the exhaust head 21 (lll lud

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and passes theiethrough into the tail pipe 19 as above outlined. From the foregoing description, it is apparent that the mutlier is strikingly free from batiles and the like and permits aA free movement of the gas therethrough without restrictions that would create undue back pressure.

Referring now to Figs. 3 and 4, the intake pipe 12 is carried farther back into the shell 10 and the tube 29 corresponding to the tube 16 in Figs. 1 and 2 is concentric with the pipe 12. The exhaust head 21 isomitted and the tail pipe 30 does not extend to within the shell but starts from the rear conical end 31. This form, while somewhat cheaper to make than that in Fig. 1, gives good results, but is not so quiet.

In Figs. 5 and 6, the shell 10 is surrounded by a cylindrical housing 33 with an appreciable space therebetween. An intake openw ing` 34 is provided at the forward end into which air may be directed from any source such as from behind the usual cooling fan (not shown) of an automobile. A discharge pipe 34 leads from the rear end of the housing 33 so that the air coming therethrough may discharge into the atmosphere or may be directed by the valve 35 through the pipe 36. The function of the housing 33 is not only to aid in cooling the shell 10 whereby a greater expansion of the gas is obtained therein, but to prevent direct radiation of sound from the shell 10.

In Figs. 5. G and 7, the exhaust head 21 is united withv the tube 16 by means of the flange 26 whereby the rear end of the tube 16 is rigidly held in position within the shell 10. The position of the various parts remains substantially as above described, with the possible exception, that in the structure shown in Fig. 5, the pocket or chamber produced behind the plate 25 forms a cushion to prevent vibrations from the plate 25 being transmitted to the rear of the tube 1G.

lhile I have described my invention in minute detail, it is obvious that many structural changes may be made therefrom without departing from the spirit of the invention, and I do not, therefore, desire to be limited to that precise form, nor any more than may be required by the following claims.

I claim:

1. In an exhaust gas silencer, a shell having a forward end and a rear end, an intake pipe entering through the forward end and eX- tending for a substantial distance to within the shell, a tube surrounding and spaced outwardly from the intake pipe for an appreciable length within the shell, said tube being closed at its rear end and open at its forward end to discharge to within said shell, and a tail pipe fixed in said shell rear lend, said intake pipe having a plurality of perforations along its length surrounded by said tube, said perforations comprising a series of holes arranged longitudinally along one side of said intake pipe, and a second. series of holes smaller in diameter than that of said first holes arranged around the pipe.

2. In an exhaust gas silencer, a shell having a. forward end and rear end, an intake pipe entering through the forward end and extending for a substantial distance to within the shell. a tube surrounding and spaced outwardly from the intake pipe for an appreciable length within the shell, said tube being closed at its rear end and open at its forward end to discharge to within said shell, and a tail pipe i'ixed in said shell rear end, said intake pipe having a plurality of perforations along its length surrounded by said tube, said perforations comprising a series of hol-cs arranged longitudinally one side of said intake pipe, and a second series of holes smaller in diameter than that of said `hrst holes arranged around the pipe, said first holes being suhstantiall.v onequarter of an inch in diameter, and said second holes being` substantially one-eighth of an inch in diameter.

3. In an exhaust gas silencer, a shell having a forward end and a rear end, an intake pipe entering through the forward end and extending for a substantial distance to within the shell, a tube surrounding and spaced outwardly from the intake pipe for an appreciable length within the shell, said tube being closed at its rear end and open at its forward end to discharge to within said shell, and a tail pipe fixed in said shell rear end, said intake pipe having a plurality of perforations along its length surrounded by said tube, said perforations comprising a series of holes arranged longitudinally along one side of said intake pipe, and a second series of holes smaller in diameter than that of said first holes arranged around the pipe, said first holes being substantially one-quarter of an inch in diameter, and said second holes being' substantially one-eighth of an inch in diameter, said two sizes of holes being in the proportion of thirty per cent larger holes and seventy per cent smaller holes.

4. In an exhaust gas silencer, a shell having a forward end and a. rear end, an intake pipe entering through the forward end and extending for a substantial distance to within the shell, a tube surrounding and spaced outwardly from the intake pipe for au appreciable length within the shell, said tube being closed at its rear end and open at its forward end to discharge to within said shell, circumferential beads spaced apart on the inner side of said shell, and a tail pipe lined in said shell rear end, said intake pipe having a `plurality of. perforations along its length surrounded by said tube, said forward end of the shell being formed to direct the disalong y charge from said tube rearwardly along the wall of said shell and a deflector in the rear end of the shell.

5. In an exhaust gas silencer, a shell having a forward end and a rear end, an intake pipe entering through the forward end and extending for a substantial distance to within the shell, a tube surrounding and spaced outwardly from the intake pipe for an agpreciable length within the shell, said tube being closed at its rear end and open at its forward end to discharge to within said shell, circumferential beads spaced apart on the inner side of said shell, and a tail pipe fixed in said shell rear end, said intake pipe having a plurality of perforations along its length surrounded by said tube, said tail pipe projecting` for a substantial distance to within said shell, and said rear end of the shell converging rearwardly from the shell and inwardly to said tail pipe, a deflector carried on the tail pipe within said shell having its outer' edge terminating` in a plane lying between the rearmost of said beads in said shell and said rear end of said shell, the outer edge of said deflector extending toward said shell to leave an opening therearound and therebetween less than the height of said beads in said shell.

6. In an exhaust gas silencer, a shell having a forward end and a rear end, an intake pipe entering through the forward end and extending fo-r a substantial distance to within the shell, a tube surrounding and spaced outwardly from the intake pipe for an appreciable length within the shell, said tube being closed at its rear end and open at its forward end to discharge to within said shell, circumferential beads spaced apart on the inner side of said shell, and a tail pipe fixed in said shell rear end, said intake pipe having a plurality of perforations along its length surrounded by said tube, said tail pipe extending to within said shell, a deflector on the tail pipe, and an exhaust head on the tail )ipe within the shell.

7. In an exhaust gas silencer, a. shell having a forward end and a rear end, an intake pipe entering through the forward end and extending for a substantial distance to within the shell, a tube surrounding and spaced outwardly from the intake pipe for an appreciable length within the shell, said tube being closed at its rear end and open at its forward end to discharge to within said shell,

circumferential beads spaced apart on the inner side o-f said shell, and a tail pipe fixed in said shell rear end, said intake pipe having a plurality of perforations along its length surrounded by said tube, said tail pipe extending to within said shell, and an exhaust head on the tail pipe within the shell, and a deflector between said exhaust head and sait rear end of said shell, said deiiector having its outer edge directed toward the wall of said shell back of the last of said beads on said shell.

8. In an exhaust gas silencer, a shell having a forward end and a rear end, an intake pipe entering through the forward end and extending for a substantial distance to Withy in the shell, a tube surrounding and spaced outwardly from the intake pipe for an appreciable length within the shell, said tube being closed at its rear end and open at its forward end to discharge towithin said shell, 

